The need to extend the life of batteries and to use the power they provide more efficiently is a significant problem in a variety of contexts today. Some of the applications where this need is apparent include battery powered vehicles and battery powered electronic devices. Another application for battery power is stand-alone or self-contained electric generators. While generators can operate on a variety of power sources, including batteries and combustible fuels, batteries are often preferred for reasons discussed further herein. Efficient use of battery power is particularly important for electric generators because they are useful sources of auxiliary power for remote locations where access to the electric power grid is inconvenient or unavailable. Generators can also serve as a back up power source when the electric power grid fails.
One common use for stand-alone generators is in the trucking industry. Truckers often consume significant amounts of diesel fuel while idling in order to provide power to the truck cab. Running the truck's engine to provide power to the cab is wasteful, expensive, and harmful to the environment. In view of these negative factors, recent federal and state laws limit the number of hours per day that truckers may leave their engines idling. As a result, truckers must look to auxiliary power sources, such as stand-alone generators, to provide power to the truck's cab. A generator that uses battery power efficiently to maximize the life of the batteries is particularly useful to the trucking industry.
Other applications for stand-alone generators include use on boats, recreational vehicles, as auxiliary power sources when primary power sources fail, and as power sources in remote locations. In many of these applications, battery powered generators are preferable to those that operate on combustible fuel because the batteries are quieter and do not produce harmful emissions. However, one of the drawbacks with battery powered generators is the limited life of the batteries. Various efforts have been made to extend the useful life of batteries. For example, longer lasting batteries have been constructed with advanced battery chemistries, such as those using lithium. Another solution implemented in some applications is to simply use arrays of multiple batteries. Different power generation applications arrange the batteries in either series or parallel arrays to meet the needs of the load and to extend the life of the batteries to a limited extent.
For example, one solution is described in an article entitled “Comparison of a Synergetic Battery Pack Drive System to a Pulse Width Modulated AC Induction Motor Drive for an Electric Vehicle,” published in IEEE Transactions on Energy Conservation, vol. 14, no. 2, June 1999. The article describes a battery pack system designed to monitor and access individual sections of the battery pack to control the discharge of the battery cells. This battery pack system is designed to avoid limiting the performance of the battery pack to the weakest cell. The battery pack system relies on battery reconfiguration techniques to improve overall performance of the battery pack. However, the battery pack system relies on external sources to recharge the batteries.
Other examples in the prior art involve systems for recharging batteries, particularly in vehicles that use electric power. However, many of these prior art solutions rely on external sources of power to recharge the batteries. These solutions do not provide a means to extend the life of batteries in a stand-alone system such as a battery powered generator.
The prior art solutions are limited in their ability to efficiently manage the power capacity of multiple batteries. Accordingly, there is a need in the art for the ability to increase the useful life of combinations of batteries used to provide power. Specifically, there is a need in the art for a system and method to more efficiently use the power provided by batteries, such as those used in generators, so that the useful life of the batteries is extended. A switching method and device is needed that allows a primary battery to provide power to an external load while also recharging a secondary battery. The needed switching method and device should allow the primary battery and the secondary battery to alternate roles so that after a designated time, the secondary battery can provide power to the external load while also recharging the primary battery. There is a further need for a switching method and device that can support the power supply and charging functions for more than two batteries.